This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 4 |
| 4 | -13 |
| 5 | 36 |
| 6 | -88 |
| 7 | 197 |
| 8 | -421 |
| 9 | 895 |
| 10 | -1946 |
| 11 | 4346 |
| 12 | -9832 |
| 13 | 22140 |
| 14 | -49043 |
| 15 | 106389 |
| 16 | -226213 |
| 17 | 473366 |
| 18 | -980413 |
| 19 | 2022418 |
| 20 | -4179198 |
| 21 | 8687753 |
| 22 | -18201140 |
| 23 | 38398455 |
| 24 | -81343408 |
| 25 | 172383461 |
| 26 | -364158198 |
| 27 | 764854519 |
| 28 | -1595107695 |
| 29 | 3302884966 |
| 30 | -6796646603 |
| 31 | 13921482698 |
| 32 | -28437025029 |
| 33 | 58034908034 |